Helminth Fauna of the Dry Tortugas. 183 
The species has some suggestion of Fk. lomentaceum. 
Dimensions, in millimeters, of specimen mounted in balsam: Length 
3.5; head, flattened, breadth 0.56; length of bothria 0.40; bulbs, length 0.72, 
breadth 0.12; diameter of neck, flattened, anterior 0.38, posterior 0.56: 
proboscis, length (estimated) 3, diameter, exclusive of hooks, base 0.05, 
near apex 0.04; hooks (at base shorter and more crowded than at apex), 
length, at base 0.014, near apex 0.028. 
From spiral valve of nurse-shark (Ginglimostoma cirratum). July 
5, One, 
25. Rhynchobothrium sp. 
(Plate 10, figs. 70-74.) 
Bothria foliaceous, but with margins somewhat thickened; head much 
broader than neck; neck slender, cylindrical, enlarging at bulbs; sheaths in 
close spirals; bulbs long-oval, with retractor muscle attached at about the 
middle of the length on the median wall; proboscides long, hooks of differ- 
ent sizes and shapes. The most marked differences are to be seen in those 
hooks which are near the base of the proboscides. On one side there are 
some small, straightish spines; on the other they are much larger; long and 
nearly straight, but with an abrupt curve at the apex. A single row of these 
large hooks extends around to the opposite side a short distance from the 
base. The proboscides were not seen fully extended. So far as seen, the 
hooks on one side remain small, slender and very sharp-pointed, but grow 
larger toward the apex, so that in the completely everted proboscis the dif- 
ference between the hooks of the opposite sides is probably slight. The 
large hooks with abruptly recurved ends are confined to the basal region. 
Beyond the base the larger hooks become rather broad, in lateral view, and 
are strongly and uniformly curved. On the other hand, among the small 
hooks some distance from the base are hooks which are straightish with 
abruptly curved tips. Towards the tip of the proboscis, as may be seen 
in the retracted part, a prevailing form is a slender hook curved in two 
directions, like a letter S nearly straightened out. 
Transverse striz begin immediately below the neck. The first distinct 
segments are shorter than broad, but soon become as long as broad. They 
then rapidly and uniformly lengthen, but remain about the same breadth. 
The posterior segments are nearly ten times as long as broad, and their 
anterior ends are abruptly larger than the posterior end of the preceding 
segment. None of the segments were mature, although rudiments of repro- 
ductive organs could be made out. In the next to the last segment the 
rudiment of the cirrus bulb was a little behind the posterior third, and the 
ovary was at the posterior fifth. The anatomy of the posterior segments, 
so far as it could be made out, is much like that of R. e-vile. 
Dimensions, in millimeters, of specimen mounted in balsam: Length 15; 
length of head and neck 2.4; breadth of head 0.73; bothrium, length 0.48, 
